po 401 is egr flow insufficient detected replace the dpfe. fords are notorious for throwing the 0401 on a bad dpfe (egr sensor) also check for blockage in all your vacum hoses and egr passages. good luck, mb
On dodge Neon you turn the ignition key 3 times (without going as far as turning the engine on). Maybe samne on many if not all cars? Then the codes will blink and you'll need the ODB2 code listing. Other option is to connect an ODB2 reader on the car's connector and read the codes directly.
Could be many reasons. If there is an check engine light, have the code pulled with a ODB2 scanner from any local garage. Reference that code with what it means and you have a better idea where to look to solve the problem.